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DOI: 10.1055/s-2005-872102
Synthesis and Characterization of Chiral Imidazolium Salts
Publikationsverlauf
Publikationsdatum:
25. Juli 2005 (online)
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Abstract
Chiral imidazolium salts that can be classified as ionic liquids (ILs) were derived from the ‘chiral pool’ precursors camphor, β-pinene, and tartaric acid. ILs containing chiral imidazolium cations as well as chiral anions were synthesized. Furthermore, the anion of the IL 1-methyl-3-[(S)-2′-methylbutyl]imidazolium tosylate was substituted on an ion-exchange resin for the chiral (S)-camphorsulfonate anion thus forming the first well-characterized ‘doubly chiral’ IL.
Keywords
imidazolium salts - ionic liquids - chiral anions, chiral cations
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Presumably, methylimidazolium formation is due to Hoffmann type elimination. NMR spectroscopy of crude reaction mixtures indicated concomitant alkene formation.
12The interchange of anions of similar size, such as OTf-, sulfonates, or BF4 - in the usual CH2Cl2-H2O system is not possible.
13We found that the classical ILs BMI·BF4 or BMI·PF6 are obtained in a purer form by the ion-exchange method than by the standard CH2Cl2-H2O extraction method.